Nowadays, various spectacle lenses for vision correction are known. For example, several examples can be put forward, such as a single vision lens in which one region for seeing an area at a predetermined distance is provided, a single vision lens in which power changes as view departs from the region, and a progressive power lens (a progressive multifocal lens in this description) which includes a portion (so-called progressive portion) where power changes continuously with respect to above two lenses.
For example, a progressive power lens according to PTL 1 includes: a distance portion which has distance power for distance vision; a near portion which has near power for near vision; and a progressive portion which exists between the distance portion and the near portion. In the spectacle lenses according to PTL 1, the distance portion and the near portion each have a respective prism, of which power is different from each other. A prism is provided as a prescription to correct visual symptoms of a user, such as strabismus, heterophoria and fixation disparity. Hereafter this prism is called a “prescription prism”. In paragraph [0004] of PTL 1, it is mentioned that double vision and poor depth perception may be experienced if the prisms of both eyes are incorrectly prescribed. An object of PTL 1 is to provide correctly prescribed prisms to progressive multifocal lenses, so that binocular vision can be comfortably exhibited in both the distance vision and near vision (paragraph [0005] in PTL 1).